Erhan 2008.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 4 groups, monoprophylaxis
Participants	Baseline characteristics Placebo (group 1) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 20 Received treatment (n): NA Analysed (n): 20 Age (mean ± SD, median (IQR), median (range)): 52.5 ± 13.9 Weight (mean ± SD, median (IQR), median (range)): 63.9 ± 11.2 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 70 Non‐smoker (%): 100 History of PONV/motion sickness (%): NA/0 Type of general anaesthesia: inhalational anaesthesia (isoflurane) Duration of anaesthesia or surgery (in min; as mean or median): 93 Use of perioperative opioids (if yes, which?): 2 µg/kg fentanyl for induction Type of surgery: laparoscopic cholecystectomy Ondansetron (group 2) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 20 Received treatment (n): NA Analysed (n): 20 Age (mean ± SD, median (IQR), median (range)): 50.3 ± 14.6 Weight (mean ± SD, median (IQR), median (range)): 62.1 ± 7.9 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 85 Non‐smoker (%): 100 History of PONV/motion sickness (%): NA/0 Type of general anaesthesia: inhalational anaesthesia (isoflurane) Duration of anaesthesia or surgery (in min; as mean or median): 82 Use of perioperative opioids (if yes, which?): 2 µg/kg fentanyl for induction Type of surgery: laparoscopic cholecystectomy Granisetron (group 3) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 20 Received treatment (n): NA Analysed (n): 20 Age (mean ± SD, median (IQR), median (range)): 50.1 ± 13.0 Weight (mean ± SD, median (IQR), median (range)): 61.2 ± 5.7 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 85 Non‐smoker (%): 100 History of PONV/motion sickness (%): NA/0 Type of general anaesthesia: inhalational anaesthesia (isoflurane) Duration of anaesthesia or surgery (in min; as mean or median): 93 Use of perioperative opioids (if yes, which?): 2 µg/kg fentanyl for induction Type of surgery: laparoscopic cholecystectomy Dexamethasone (group 4) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 20 Received treatment (n): NA Analysed (n): 20 Age (mean ± SD, median (IQR), median (range)): 53.4 ± 7.6 Weight (mean ± SD, median (IQR), median (range)): 62.9 ± 5.8 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 65 Non‐smoker (%): 100 History of PONV/motion sickness (%): NA/0 Type of general anaesthesia: inhalational anaesthesia (isoflurane) Duration of anaesthesia or surgery (in min; as mean or median): 85.8 Use of perioperative opioids (if yes, which?): 2 µg/kg fentanyl for induction Type of surgery: laparoscopic cholecystectomy Included criteria: scheduled for laparoscopic cholecystectomy with general anaesthesia, between 21 and 75 years of age (mean 51.5 years) Excluded criteria: ASA III or IV; over 75 years of age; body mass index > 30; pregnancy; smoking; signs of gastrointestinal, endocrine, renal, hepatic, or immunological disease; use of opioids or tranquillizers less than 1 week before the operation; treatment with steroids; history of alcohol or drug abuse; history of motion sickness; preoperative diagnosis of gallbladder empyema and previous endoscopic sphincterotomy for common bile duct stones; conversion to open cholecystectomy Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, non‐smoker, history of motion sickness, perioperative opioids): no; (history of PONV): unclear
Interventions	Intervention characteristics Placebo (group 1) Dose: 0.9% NaCl Time point of administration: 15 minutes before induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): metoclopramide 10 mg IV Ondansetron (group 2) Dose: 4 mg Time point of administration: 15 minutes before induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): metoclopramide 10 mg IV Granisetron (group 3) Dose: 3 mg Time point of administration: 15 minutes before induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): metoclopramide 10 mg IV Dexamethasone (group 4) Dose: 8 mg Time point of administration: 15 minutes before induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): metoclopramide 10 mg IV
Outcomes	Vomiting (0 to 24 hours) Outcome type: dichotomous outcome Vomiting (0 to 6 hours) Outcome type: dichotomous outcome Vomiting (6 to 12 hours) Outcome type: dichotomous outcome Nausea (0 to 24 hours) Outcome type: dichotomous outcome Complete response (no PONV) in 24 hours Outcome type: dichotomous outcome Adverse events (general notes in the publication, 24 hours' observation) Outcome type: general notes on side effects
Identification	Sponsorship source: NA Country: Turkey Setting: inpatient, single‐centre Author's name: Yamac Erhan Institution: Department of Surgery, Faculty of Medicine, Celal Bayar University, Manisa 45040, Turkey Email: yamacerhan@yahoo.com Address: Department of Anesthesiology, Faculty of Medicine, Ege University, 35100 Izmir, Turkey Duration of study: NA Language: English Study's primary outcome: NA Trial registry number: NA
Notes	None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "patients were randomly divided into four groups" Judgement comment: no further information on sequence generation provided
Allocation concealment (selection bias)	Unclear risk	Judgement comment: no statement
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "study medications were prepared by a technician anesthetist in identical 5 ml syringes and administered in a double‐blind fashion"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "the incidence of nausea and vomiting was recorded during three assessment periods, 0–6 h, 6–12 h, and 12–24 h, by nursing staff without knowledge of which antiemetic the patients had received. Both..."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "all 80 patients enrolled in the study had their surgical procedures completed"
Selective reporting (reporting bias)	Unclear risk	Judgement comment: no reference to a study protocol or trial registry number reported
Other bias	Unclear risk	Quote: "the mean values for age, weight, height, time of surgery, and time of anesthesia are given in Table 1. Groups were comparable with respect to demographic data, time of surgery, and time of anesthesia" Judgement comment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, non‐smoker, history of motion sickness, perioperative opioids): no; (history of PONV): unclear